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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Calculation of isotropic Compton profiles with Gaussian basis sets.
Jussi Lehtola1, Mikko Hakala, Juha Vaara
1Department of Physics, University of Helsinki, Helsinki, Finland. jussi.lehtola@helsinki.fi
Physical Chemistry Chemical Physics : PCCP
|February 2, 2011
Summary
This study introduces an adaptive algorithm for calculating electron momentum density via isotropic Compton profiles (ICP). Accurate ICP calculations, crucial for interpreting X-ray scattering data, require diffuse basis functions and triple-ζ quality basis sets for light elements.
Area of Science:
- Computational Chemistry
- Quantum Mechanics
- Materials Science
Background:
- Isotropic Compton profiles (ICP) quantify electron momentum density.
- ICP are experimentally measured using inelastic X-ray scattering with synchrotron radiation.
- Accurate theoretical calculation of ICP is essential for interpreting experimental data.
Purpose of the Study:
- To develop an adaptive algorithm for calculating ICP for any Gaussian basis set.
- To investigate the impact of basis set choice and theoretical methods on ICP accuracy.
- To establish guidelines for basis set selection in ICP calculations.
Main Methods:
- Implementation of an adaptive algorithm for ICP calculation.
- Utilizing density-functional theory, Hartree-Fock, and post-Hartree-Fock methods.
- Employing Dunning-type ((d-)aug-)cc-p(C)VXZ basis sets for calculations on water and helium systems.
Main Results:
- Demonstrated the critical importance of diffuse basis functions for accurate ICP.
- Showcased convergence behavior of ICP with respect to basis set size and level of theory.
- Identified triple-ζ quality basis sets with diffuse functions as necessary for reliable results.
Conclusions:
- The developed adaptive algorithm provides a robust method for ICP computation.
- Diffuse basis functions are indispensable for achieving converged ICP values.
- Recommendations for basis set selection are provided for accurate ICP calculations of light elements, aligning with experimental feasibility.
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